Manufacture of tubes by the push bench process



Jan. 8, 1935. c. w. LITTLER MANUFACTURE OF TUBES BY THE PUSH BENCH PROCESS Fi led Feb. 4, 1931 INVENTQR c w. Um, h

LEE-iii Patented Jan. 8, 1935 MANUFACTURE OF TUBES BY THE PUSH BENCH PROCESS cal-1w. Littler, Pittsburgh, re. Application February 4, 1931, Serial No. 513,307

12 Claims. (Cl. 29-33) This invention relates to the manufacture of seamless tubes and particularly to certain improvements in the push bench process of manufacture.

In the manufacture of tubes by the push bench process a heated billet is subjected to the action of a plunger which penetrates the axis of the billet for a material distance, forming a thickwalled cylindrical shell closed at one end. This shell is placed over the end of along mandrel bar and the mandrel is pushed through a series of ring dies successively decreasing in diameter, which dies reduce the wall thickness of the shell and elongate it into a tube having one end closed. The tube is stripped from the mandrel and subjected to desired finishing operations, the mandrel itself being returned to a position in alinement with the ring dies ready to receive another shell.

The pushing of the shell through the ring dies generates a large amount of heat and the front end of the mandrel particularly becomes very hot and may be deformed. The front end may be enlarged or bent out of alinement with the remainder of the mandrel. If such mandrel is again employed, the interior finish of the tube may be marred and the wall thickness may be non-uniform. If the deformation of the mandrel head is by way of enlargement, difficulty will be encountered in stripping the tube from the mandrel.

Mandrels for this use are generally made of special alloy steels at high expense, and it is desirable to keep the number'on hand down to a relatively low figure. It is also desirable to so employ the mandrels that they will be of uniform and constant temperature at the initiation of each tube forming operation. It will be understood that in the push bench process, particularly as applied to tubes of longer lengths, great care must be employed in heating and maintaining uniform at all points the temperature of the billet or shell. The mandrel is attached at its rear end to a pusher. Of itself, it does not bearcolder side, being less plastic, will tend to force the mandrel sidewise, resulting in an eccentric tube. It is therefore highly important to eliminate any tendency towardnon-uniform cooling or chilling of theshell by the mandrel.

I overcome these difiiculties by providing, in

the return path of the mandrel from the stripping means to the push bench proper, means for heating, sizing and straightening the mandrel. The mandrels thus treated are straight, of uniform size from end to end, and of uniform temperature, thus improving the quality of the product and eliminating delays and defective tubes such as result from the employment of misshapen or non-uniformly heated mandrels.

The accompanying drawing is a plan view illustrating the layout of a plant for the manufacture of tubes by my improved process. In the drawing there is shown a heating furnace 2 provided with a pusher 3, whereby square billets 4, cut to length, are fed through the furnace continuously. Openings 5 having doors 6 are provided so that workmen may roll the leading billets over, thus separating them from the file of billets fed by the pusher and facilitating uniform heating. The billets are taken from the furnace through doors 7 to transfer cars 8 moving .on tracks 9, whereby they are supplied to a press indicated generally at 10. The press .has a cylindrical die 11 into which the square billets are dropped. The billets, while in the die, are subjected to the action of a piercing plunger which partially penetrates the axis of the billet, the displaced metal filling the segmental spaces between the die and the square billet, thus forming a thick-walled cylindrical shell which is closed at one end.

The shell is ejected from the die 11 and supplied to a transfer arm 12 which moves in the path indicated by the dotted line P. The'arm 12 is shown in position alongside the push bench 13 and a shell S is shown lying on the push bench ready to be formed into a tube. A mandrel 14,

lying on the push bench, is fed into'the open end of the shell S. The mandrel is connected at 15 to a pusher 16 extending forwardly from a rack 17 driven by a motor 18. When the motor 18 is energized, the mandrel 14 with the shell S thereon is pushed through a series of ring dies 19 mounted in a ring bench 20. The dies are of successively smaller diameter and are effective for reducing the wall thickness of the shell and elongating it rearwardly over the mandrel.

After the mandrel has been pushed entirely through the ring dies, it is disconnected from the pusher 16 and lies on conveyor rollers 21. The mandrel with the tube thereon is fedthrough reeling rolls 22 which loosen the tube from the mandrel bar and deliver it to table rollers 23. It is then fed sidewise onskids 24 to table rollers 25 in alinement with a stripping die 26. A tongs 2'7, secured to a chain 28, engages the rear end of'the mandrel bar and pulls it to the left as viewed in the drawing, the chain being pulled by a motor 29. The die 26 engages the end of the tube and strips it from the mandrel bar. The

closed-end tube is fed sidewise over skids 30 to table rollers 31 which feed the tube to a hot saw,

bar rolls slowly therethrough. They are also arranged at an angle to the direction of travel of the mandrels so that they will not give rise to any chilled bands around the mandrel. The furnace will be maintained at a temperature sufficient to render the mandrels substantially uniform in temperature but below a point where the physical properties of the mandrel are impaired.

As the mandrels issue from the furnace they are received by table rollers 41 which feed the mandrel to a sizing mill 42. The sizing mill reduces any enlargement at the head of the mandrel and makes it of uniform diameter from end to end. The sized mandrel is then fed through a straightening machine 43 to table rollers 44, skids 45 and table rollers 46, from which the mandrels are successively supplied by means of arms 4'7 to skids 48 over which the mandrels roll onto the ring bench 13. i

The table rollers 46 are in alinement with th rollers 37 so that, if desired, the mandrels may be by-passed around the furnace, the sizing mill and the straightening machine.

It may be desirable in certain cases to so arrange the straightening machine or the sizing mill that the front end of the mandrel will be fed first therethrough. For example, with certain types of straightening machines, difficulty may be encountered in the formation of a so- -cal1ed goose-neck, which is a departure from true straightness near one end of the piece being straightened. A goose-neck is highly undesirable in a mandrel, but if it is to be tolerated at all it is best that it should, be on the rear end rather than the front end of the mandrel.

I have illustrated and described a present preferred embodiment of the invention. It will be understood, however, that this is by way of example only, and thatthe invention may be otherwise embodied or practiced within the scope of the following claims.

I claim: v

1. In the push bench process of tube manufacture, the steps consisting informing a tube on on a mandrel, stripping the tube therefrom, heating the mandrel to substantially uniform temperature to prevent formation of non-uniform tubes by reason of non-uniform mandrel tem: perature, sizing the mandrel, and again forming a tube thereon.

3. In the push bench process of tube manufacture, the steps consisting in forming a tube on the mandrel, stripping the tube therefrom, heating the mandrel to substantially uniform temperature to prevent formation of non-uniform tubes by reason of non-uniform mandrel temperaturebut below a temperature which will impair the physical properties of the mandrel to to prevent formation ofnon-uniform tubes by reason of non-uniform mandrel temperature, and again forming a tube thereon.

6. In combination with a push bench, stripping means for removing formed tubes from the mandrels over which they are formed in the push bench, a conveyor for returning the mandrels from the stripping means to the push bench, and mandrel heating means in the return path of the mandrels.

7. In combination with a push bench, stripping means for removing formed tubes from the mandrels over which they are formed in the push bench, a conveyor for returning the mandrels from the stripping means to the push bench, and straightening means in the return path of the mandrels.

8. In combination with a push bench, stripping means for removing formed tubes from the mandrels over which they are formed in the push bench, a conveyor for returning the mandrels from the stripping means to the push bench, and mandrel heating and sizing means in the return path of the mandrels.

9. In combination with a push bench, stripping means for removing formed tubes from the mandrels over which they are formed in the push bench, a conveyor for returning the mandrels from the stripping means to the push bench, mandrel heating means in the return path of the mandrels, and a conveyor for by-passing the mandrel heating means.

10. In combination with apush bench, stripping means for removing formed tubes from the mandrels over which they are formed in the push bench, a conveyor for returning the mandrels from the stripping means to the push bench, sizing means in the return path of the mandrels, and a conveyor for by-passing the sizing means.

11. In combination with a push bench, stripping means for removing formed tubes from the mandrels over which they are formed in. the

push bench, a conveyor for returning the man-- drels from the stripping means to the push bench,

straightening means in the return pathof the mandrels, and a conveyor for by-passing the straightening means.

12. In combination with a push bench, stripping means for removing formed tubes from the mandrels over which they are formed in the push bench, means for returning the mandrels from the .stripping means to the push bench, and heating means for the mandrels adapted to heat the same prior to their return to the push bench, said heating means comprising a heating chamber-0f a size suflicient to receive an entire mandrel so as to heat such mandrel uniformly throughout.

' CARL W. LI'I'I'LER. 

